The enquiry is broadly directed toward analysis of events involved in transduction of stimulus (whether neurotransmitter, hormone or action potential) into secretory response in various cells. Some cells, of which the adrenal chromaffin cell is the archetype, show membrane potential changes in response to secretagogues or inhibitors. This behavior is also being demonstrated in cells of the adenohypophysis from various species including mammals, teleosts, and lizards. The electrical properties of such endocrine cells are being analyzed, and attempts are being made to correlate such activity with secretory control. An aim is to analyze the involvement of Ca ions in stimulus-secretion coupling, particularly as it relates to exocytosis, and to define the cellular mechanisms that are used to achieve the rise in intracellular Ca ion concentration that is suspected of initiating secretory responses. The methods involve studies on isolated cells for the most part exposed to various ionic and pharmacological manipulations and electrophysiological analysis.